Semiconductor light emitting device having roughness layer

ABSTRACT

A semiconductor light emitting device is provided, including a substrate, a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer that includes a top surface and a bottom surface. The device includes a first roughness layer having a random horn shape and formed with irregular intervals, a second roughness layer, and at least one of a first AlGaN based semiconductor layer and a second AlGaN based semiconductor layer. The second conductive semiconductor layer includes a plurality of apexes on the top surface, where the distance between at least two apexes is of about 0.3 μm to about 1.0 μm. The second roughness layer includes a lower surface having a shape corresponding to the top surface of the second conductive semiconductor layer. The second roughness layer includes an upper surface having a shape corresponding to a top surface of the first roughness layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of copending application Ser. No.12/883,554 filed on Sep. 16, 2010, which claims priority to copendingContinuation application Ser. No. 12/340,354 filed on Dec. 19, 2008 (nowU.S. Pat. No. 7,821,024 issued Oct. 26, 2014), which claims priorityunder 35 U.S.C. 119(a) to Korean Patent Application No. 10-2007-0133919filed on Dec. 20, 2007. The contents of all these applications arehereby incorporated by reference in their entirety.

BACKGROUND

The present disclosure relates to a semiconductor light emitting device.

Group III-V nitride semiconductors have been variously applied to anoptical device such as blue and green light emitting diodes (LED), ahigh speed switching device, such as a MOSFET (Metal Semiconductor FieldEffect Transistor) and an HEMT (Hetero junction Field EffectTransistors), and a light source of a lighting device or a displaydevice.

The nitride semiconductor is mainly used for the LED (Light EmittingDiode) or an LD (laser diode), and studies have been continuouslyconducted to improve the fabrication process or light efficiency of thenitride semiconductor.

SUMMARY

Embodiments provide a semiconductor light emitting device comprising asecond conductive semiconductor layer with a dual roughness structure.

Embodiments provide a semiconductor light emitting device comprising asecond conductive semiconductor layer with a horn-shaped dual roughnessstructure.

Embodiments provide a semiconductor light emitting device, which iscapable of enhancing external quantum efficiency by forming ahorn-shaped dual roughness structure in a second conductivesemiconductor layer.

An embodiment provides a semiconductor light emitting device comprising:a first conductive semiconductor layer; an active layer on the firstconductive semiconductor layer; and a second conductive semiconductorlayer comprising a dual roughness structure on the active layer.

An embodiment provides a semiconductor light emitting device comprising:a first conductive semiconductor layer; an active layer on the firstconductive semiconductor layer; and a second conductive semiconductorlayer on the active layer, wherein the second conductive semiconductorlayer comprises: a first semiconductor layer comprising a shape ofmultiple horns; and a roughness layer ohmic-contacted on the firstsemiconductor layer.

An embodiment provides a semiconductor light emitting device comprising:a substrate; a first conductive semiconductor layer on the substrate; anactive layer on the first conductive semiconductor layer; and a secondconductive semiconductor layer comprising a dual roughness structure ofa shape a multiple horns on the active layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a semiconductor light emitting deviceaccording to a first embodiment, while FIG. 1A is a side sectional viewof a semiconductor light emitting device according to an embodimentrelated to the first embodiment.

FIGS. 2 through 7 are sectional views illustrating a method forfabricating a semiconductor light emitting device according to a firstembodiment.

FIG. 8 is a side sectional view of a semiconductor light emitting deviceaccording to a second embodiment.

FIG. 9 is a side sectional view of a semiconductor light emitting deviceaccording to a third embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a semiconductor light emitting device according to theembodiment will be described with reference to the accompanyingdrawings. In the description of the embodiment, it will be understoodthat, when a layer (or film), a region, a pattern, or a structure isreferred to as being “on(above/over/upper)” or “under(below/down/lower)”another substrate, another layer (or film), another region, another pad,or another pattern, it can be directly on the other substrate, layer (orfilm), region, pad or pattern, or intervening layers may also bepresent. Furthermore, it will be understood that, when a layer (orfilm), a region, a pattern, a pad, or a structure is referred to asbeing “between” two layers (or films), regions, pads, or patterns, itcan be the only layer between the two layers (or films), regions, pads,or patterns or one or more intervening layers may also be present. Thus,it should be determined by technical idea of the invention.

FIG. 1 is a side sectional view of a semiconductor light emitting deviceaccording to a first embodiment.

Referring to FIG. 1, a semiconductor light emitting device 100 comprisesa substrate 110, a buffer layer 120, a first conductive semiconductorlayer 130, an active layer 140, a second conductive semiconductor layer150 having dual roughness 152 and 156, a first electrode 171, and asecond electrode 173.

The substrate 110 may be formed of a material selected from the groupconsisting of sapphire (Al₂O₃), GaN, SiC, ZnO, Si, GaP, and GaAs.Concave-convex patterns may be formed on the substrate 110, but thepresent invention is not limited thereto.

The buffer layer 120 is formed on the substrate 110. The buffer layer120 is a layer for reducing a lattice constant difference from thesubstrate 110. The buffer layer 120 may be formed to a predeterminedthickness (for example, about 140 Å to about 1,000 Å) by selectivelyusing GaN, AlN, AlGaN, InGaN, or AlInGaN.

An undoped semiconductor layer (not shown) may be formed on the bufferlayer 120 or the substrate 110. The undoped semiconductor layer (notshown) may comprise an undoped GaN-based layer. Neither of the bufferlayer 120 and the undoped semiconductor layer (not shown) may be formedon the substrate 110, or at least one of them may be formed on thesubstrate 110.

At least one first conductive semiconductor layer 130 is formed on thebuffer layer 120. The first conductive semiconductor layer 130 is asemiconductor layer doped with a first conductive dopant. The firstconductive semiconductor layer 130 may be formed of a semiconductormaterial having a composition formula of In_(x)Al_(y)Ga_(1−x−y)N (0≦x≦1,0≦y≦1, 0≦x+y≦1), for example, InAlGaN, GaN, AlGaN, InGaN, AlN, or InN.When the first conductive semiconductor layer 130 is an N-typesemiconductor layer, the first conductive dopant is an N-type dopant,such as Si, Ge, or Sn.

The active layer 140 is formed on the first conductive semiconductorlayer 130. The active layer 140 may have a single quantum well structureor a multiple quantum well structure. The active layer 140 may be formedof InGaN/GaN or AlGaN/GaN by using group III-V compound semiconductors.

The active layer 140 is formed of a material having a bandgap energyaccording to a light wavelength at which light is emitted. For example,in the case of a blue light emission having a wavelength range from 460nm to 470 nm, the active layer 140 may be formed in a single or multiplequantum well structure at a period of an InGaN well layer/GaN barrierlayer. The active layer 140 may comprise a material emitting a coloredlight such as a blue wavelength light, a red wavelength light, and agreen wavelength light. A conductive clad layer 140A and/or 140B may beformed over and/or under the active layer 140 as shown in FIG. 1A, andthe conductive clad layer 140A and/or 140B comprises an AlGaN-basedlayer.

The second conductive semiconductor layer 150 is formed on the activelayer 140. The second conductive semiconductor layer 150 is asemiconductor layer doped with a second conductive dopant. The secondconductive semiconductor layer 150 may be formed of a semiconductormaterial having a composition formula of In_(x)Al_(y)Ga_(1−x−y)N (0≦x≦1,0≦y≦1, 0≦x+y≦1), for example, InAlGaN, GaN, AlGaN, InGaN, AlN, or InN.When the second conductive semiconductor layer 150 is a P-typesemiconductor layer, the second conductive dopant is a P-type dopant,such as Mg, Zn, Ca, Sr, or Ba.

The first conductive semiconductor layer 130, the active layer 140, andthe second conductive semiconductor layer 150 serve as a light emittingstructure. The light emitting structure may be formed in one of an N-Pjunction structure, a P-N junction structure, an N-P-N junctionstructure, and a P-N-P junction structure.

The second conductive semiconductor layer 150 comprises a firstsemiconductor layer 151 and a roughness layer 155.

The first semiconductor layer 151 is a P-type semiconductor layer dopedwith a second conductive dopant and may be formed of InAlGaN, GaN,AlGaN, InGaN, AlN, or InN. The first semiconductor layer 151 has a firstroughness 152 on the top surface thereof, and the first roughness 152may be formed in a shape of multiple horns.

The first roughness 152 may have a structure in which horn-shaped apexpatterns and inverse-horn-shaped valley patterns are alternatelyarranged.

The first roughness 152 may have a height (H) of about 0.5 μm to about1.2 μm and a diameter (D) of about 0.3 μm to about 1.0 μm. The height(H) of the first roughness 152 may be that of the horn-shaped apexpattern, and the diameter (D) of the first roughness 152 may be lengthbetween two the apexes or between two valleys. The first roughness 152may have a horn shape, a polygonal horn shape, or a random horn shape,and may be formed at irregular intervals.

The roughness layer 155 is formed on the first semiconductor layer 151.The roughness layer 155 is a P-type semiconductor layer doped with asecond conductive dopant and may be formed of InAlGaN, GaN, AlGaN,InGaN, AlN, or InN.

The roughness layer 155 is ohmic-contacted with the first semiconductorlayer 151 and may be formed to a predetermined thickness of about 1,000Å to about 2,000 Å.

The roughness layer 155 is formed with a second roughness 156. Thesecond roughness 156 may be formed in the same shape as the firstroughness 152. The second roughness 156 may have a structure in whichhorn-shaped apex patterns and inverse-horn-shaped valley patterns arearranged regularly or irregularly.

The first semiconductor layer 151 and the roughness layer 155 may beformed of the same semiconductor materials or the differentsemiconductor materials.

The second electrode 173 is formed on the roughness layer 155 of thesecond conductive semiconductor layer 150, and the second electrode 173may have predetermined patterns. The first electrode 171 may be formedon or electrically connected to the first conductive semiconductor layer130.

By forming the first roughness and the second roughness having a shapeof multiple horns in the second conductive semiconductor layer 150,external quantum efficiency can be enhanced. That is, the horn-shapedfirst rough 152 and the horn-shaped second roughness 156 change theincident angle of light emitted from the active layer 140, therebyenhancing light emission efficiency.

FIGS. 2 through 7 are sectional views illustrating a method formanufacturing a semiconductor light emitting device according to a firstembodiment.

Referring to FIG. 2, a buffer layer 120, a first conductivesemiconductor layer 130, an active layer 140, and a first semiconductorlayer 151A of a second conductive semiconductor layer are formed on asubstrate 110.

The substrate 110 may be formed of a material selected from the groupconsisting of sapphire (Al₂O₃), GaN, SiC, ZnO, Si, GaP, and GaAs. Thebuffer layer 120 is formed on the substrate 110 and may be formed ofGaN, AlN, AlGaN, InGaN, or AlInGaN. An undoped semiconductor layer (notshown) may be formed on the buffer layer 120 or the substrate 110. Theundoped semiconductor layer (not shown) may comprise an undopedGaN-based layer. Neither of the buffer layer 120 and the undopedsemiconductor layer (not shown) may be formed on the substrate 110, orat least one of them may be formed.

At least one first conductive semiconductor layer 130 is formed on thebuffer layer 120. The first conductive semiconductor layer 130 maycomprise an N-type semiconductor layer. The first conductivesemiconductor layer 130 may be formed of a semiconductor material havinga composition formula of In_(x)Al_(y)Ga_(1−x−y)N (0≦x≦1, 0≦y≦1,0≦x+y≦1), for example, InAlGaN, GaN, AlGaN, InGaN, AlN, or InN. Thefirst conductive semiconductor layer 130 comprises an N-type dopant,such as Si, Ge, or Sn.

The active layer 140 is formed on the first conductive semiconductorlayer 130. The active layer 140 may have a single quantum well structureor a multiple quantum well structure. The active layer 140 may be formedof InGaN/GaN or AlGaN/GaN by using group III-V compound semiconductors.The active layer 140 may comprise a material emitting a colored lightsuch as a blue wavelength light, a red wavelength light, and a greenwavelength light.

A conductive clad layer (not shown) may be formed over and/or under theactive layer 140. The conductive clad layer (not shown) comprises anAlGaN-based layer.

The first semiconductor layer 151A of the second conductivesemiconductor layer is formed on the active layer 140. The firstsemiconductor layer 151A may comprise a P-type semiconductor layer. Thefirst semiconductor layer 151A may be formed of a semiconductor materialhaving a composition formula of In_(x)Al_(y)Ga_(1−x−y)N (0≦x≦1, 0≦y≦1,0≦x+y≦1), such as InAlGaN, GaN, AlGaN, InGaN, AlN, or InN. The firstsemiconductor layer 151A may comprise a P-type dopant such as Mg, Zn,Ca, Sr, or Ba. The first semiconductor layer 151A may be formed to apredetermined thickness of about 0.7 μm to about 1.5 μm.

Referring to FIGS. 3 and 4, a removal layer 160 is formed on the firstsemiconductor layer 151A. The removal layer 160 is formed in a thin filmtype by selectively using indium tin oxide (ITO), indium zinc oxide(IZO), aluminum zinc oxide (AZO), silver (Ag), and aluminum (Al).

A first etching process is performed on the removal layer 160. The firstetching process uses a wet etchant (for example, HCl solution). Theremoval layer 160 is formed in a shape of multiple island patterns 162by a wet etching process.

The island patterns 162 may have an embossing shape, a semisphericalshape, or a convex lens shape, or may be formed regularly or irregularlywith an irregular size and a random shape. The shape and size of theisland patterns 162 may be different according to a material of theremoval layer 160 or an etching degree.

Referring to FIGS. 4 and 5, a second etching process is performed on theisland patterns 162. The second etching process may be performed by adry etching process.

The second etching process may be performed from the multiple islandpatterns 162 to a predetermined portion of the first semiconductor layer151A.

The dry etching process may be performed by selectively using anInductively Coupled Plasma (ICP) apparatus, a Reactive Ion Etching (RIE)apparatus, a Capacitively Coupled Plasma (CCP) apparatus, and anElectron Cyclotron Resonance (ECR) apparatus.

An etching depth of the first semiconductor layer 151A is changedaccording to a material difference (strength difference) and a thicknessdifference of the island patterns 162. Accordingly, the firstsemiconductor layer 151 has a first roughness 152 having a shape ofmultiple horns on the top surface thereof.

The first roughness 152 of the first semiconductor layer 151 is formedin an apex/valley patterns. The valley patterns are formed by arelatively thin island pattern region, and the apex patterns are formedby a relatively thick island pattern region.

The first roughness 152 of the first semiconductor layer 151 may beformed in a horn shape, a polygonal horn shape, or a random horn shape,and may be formed at dense intervals.

The first roughness 152 may have a height (H) of about 0.5 μm to about1.2 μm and a diameter (D) of about 0.3 μm to about 1.0 μm.

Referring to FIG. 6, a roughness layer 155 is formed on the firstsemiconductor layer 151. The first semiconductor layer 151 and theroughness layer 155 define a second conductive semiconductor layer 150.

The roughness layer 155 may be a P-type semiconductor layer. Theroughness layer 155 may be formed of a semiconductor material having acomposition formula of In_(x)Al_(y)Ga_(1−x−y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1),for example, InAlGaN, GaN, AlGaN, InGaN, AlN, or InN. The roughnesslayer 155 may comprise a P-type dopant such as Mg, Zn, Ca, Sr, or Ba.

The roughness layer 155 may be formed to a predetermined thickness ofabout 1,000 Å to about 2,000 Å and is ohmic-contacted with the firstsemiconductor layer 151. A second roughness 156 having the same shape asthe first roughness 152 is formed in the roughness layer 155.

The second conductive semiconductor layer 150 may have a structure inwhich a dual structure of the first roughness 152 and the secondroughness 156 is formed in a horn shape.

Referring to FIG. 7, a mesh etching process is performed to expose aportion of the first conductive semiconductor layer 130.

A first electrode 171 is formed on the first conductive semiconductorlayer 130, and a second electrode 173 is formed on the second conductivesemiconductor layer 150.

In the semiconductor light emitting device 100 according to the currentembodiment, the dual structure of the horn-shaped roughness 152 and 156is formed in the second conductive semiconductor layer 150. Thus, theincident angle of light emitted from the active layer 140 can bechanged, thereby enhancing external quantum efficiency.

FIG. 8 is a side sectional view of a semiconductor light emitting deviceaccording to a second embodiment. In the first and second embodiments,like reference numerals refer to like elements and duplicate descriptionwill be omitted.

Referring to FIG. 8, the semiconductor light emitting device 100Acomprises a substrate 110, a buffer layer 120, a first conductivesemiconductor layer 130, an active layer 140, a second conductivesemiconductor layer 150 having dual roughness 152 and 156, a transparentelectrode layer 170, a first electrode 171, and a second electrode 173.

The transparent electrode layer 170 is formed on the second conductivesemiconductor layer 150 and may have a roughness structure.

The transparent electrode layer 170 may have a roughness with a shape ofmultiple horns along the roughness layer 155 of the second conductivesemiconductor layer 150. Accordingly, a triple structure of horn-shapedroughness may be formed on the active layer 140.

The transparent electrode layer 170 may comprise at least one of indiumtin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO),indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO),indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tinoxide (ATO), ZnO, RuOx, TiOx, IrOx, and SnO₂.

The second electrode 173 may be formed on the roughness layer 155 of thesecond conductive semiconductor layer 150, or may be formed on thetransparent electrode layer 170 and/or the roughness layer 155.

FIG. 9 is a side sectional view of a semiconductor light emitting deviceaccording to a third embodiment. In the first and third embodiments,like reference numerals refer to like elements and duplicate descriptionwill be omitted.

Referring to FIG. 9, the semiconductor light emitting device 100Bcomprises a substrate 110, a buffer layer 120, a first conductivesemiconductor layer 130, an active layer 140, a second conductivesemiconductor layer 150 having dual roughness 152 and 156, a thirdconductive semiconductor layer 170, a first electrode 171, and a secondelectrode 173.

The third conductive semiconductor layer 175 may comprise an N-typesemiconductor layer or a P-type semiconductor layer. For example, whenthe first conductive semiconductor layer 130 is an N-type semiconductorlayer, the third conductive semiconductor layer 175 may be an N-typesemiconductor layer. When the first conductive semiconductor layer 130is a P-type semiconductor layer, the third conductive semiconductorlayer 175 may be a P-type semiconductor layer.

The third conductive semiconductor layer 175 may have a roughness with ashape of multiple horns along the roughness layer 155 of the secondconductive semiconductor layer 150. Accordingly, a triple structure ofhorn-shaped roughness may be formed on the active layer 140.

Furthermore, a transparent electrode layer (not shown) may be formed onthe third conductive semiconductor layer 175, and the transparentelectrode layer (not shown) can diffuse a current to a whole region.

The second electrode 173 may be formed on the third conductivesemiconductor layer 175, but the present invention is not limitedthereto.

The semiconductor light emitting device according to the currentembodiment may be formed in a P-N structure, an N-P structure, an N-P-Nstructure, and a P-N-P structure. Accordingly, the second conductivesemiconductor layer 150 may be implemented with an N-type semiconductorlayer or a P-type semiconductor layer.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is comprised in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A semiconductor light emitting device,comprising: a substrate; a first conductive semiconductor layer on thesubstrate; an active layer on the first conductive semiconductor layer;a second conductive semiconductor layer on the active layer, the secondconductive semiconductor layer including a top surface and a bottomsurface opposing to the top surface, the bottom surface being adjacentto the active layer; a first roughness layer disposed on the secondconductive semiconductor layer and including Al material, the firstroughness layer including a random horn shape and formed with irregularintervals; a second roughness layer including Ti material on the firstroughness layer; and at least one of a first AlGaN based semiconductorlayer disposed on the active layer and a second AlGaN basedsemiconductor layer disposed under the active layer, wherein the firstconductive semiconductor layer includes a first GaN layer and the secondconductive semiconductor layer includes a second GaN layer, wherein thesecond conductive semiconductor layer includes a plurality of apexes onthe top surface, the distance between at least two apexes of theplurality of apexes is of about 0.3 μm to about 1.0 μm, wherein thesecond roughness layer includes a lower surface having a shapecorresponding to the top surface of the second conductive semiconductorlayer, and wherein the second roughness layer includes an upper surfacehaving a shape corresponding to a top surface of the first roughnesslayer.
 2. The semiconductor light emitting device according to claim 1,further comprising an electrode on the second conductive semiconductorlayer, wherein the electrode has a bottom surface with a shapecorresponding to the top surface of the second conductive semiconductorlayer.
 3. The semiconductor light emitting device according to claim 1,wherein the second roughness layer is disposed directly on the firstroughness layer.
 4. The semiconductor light emitting device according toclaim 1, wherein the first roughness layer includes an upper surfacehaving a shape corresponding to the top surface of the second conductivesemiconductor layer.
 5. The semiconductor light emitting deviceaccording to claim 1, wherein the first roughness layer is asemiconductor layer.
 6. The semiconductor light emitting deviceaccording to claim 1, wherein the first roughness layer is formed of asame semiconductor material as that of the second conductivesemiconductor layer.
 7. The semiconductor light emitting deviceaccording to claim 1, wherein the first roughness layer has a thicknessof about 1000 Å to about 2000 Å.
 8. The semiconductor light emittingdevice according to claim 1, wherein a distance between one apex of theplurality of apexes and a valley that is positioned close thereto is inthe range of about 0.5 μm to about 1.2 μm.
 9. A semiconductor lightemitting device, comprising: a first conductive semiconductor layer; anactive layer on the first conductive semiconductor layer; a secondconductive semiconductor layer on the active layer; a first roughnesslayer on the second conductive semiconductor layer and including Almaterial, the first roughness layer including a random horn shape andformed with irregular intervals; and a second roughness layer on thefirst roughness layer and including Ti material, wherein a top surfaceof the second conductive semiconductor layer includes a roughness,wherein the first roughness layer includes a lower surface having ashape corresponding to the top surface of the second conductivesemiconductor layer, wherein the second roughness layer includes anupper surface having a shape corresponding to a top surface of the firstroughness layer, and wherein the second roughness layer includes a lowersurface having a shape corresponding to the top surface of the secondconductive semiconductor layer.
 10. The semiconductor light emittingdevice according to claim 9, wherein the first conductive semiconductorlayer includes a first GaN layer and the second conductive semiconductorlayer includes a second GaN layer.
 11. The semiconductor light emittingdevice according to claim 9, wherein the second conductive semiconductorlayer includes a plurality of apexes on the top surface, the distancebetween at least two apexes of the plurality of apexes is of about 0.3μm to about 1.0 μm.
 12. The semiconductor light emitting deviceaccording to claim 9, wherein a distance between one apex of theplurality of apexes and a valley that is positioned close thereto is inthe range of about 0.5 μm to about 1.2 μm.
 13. The semiconductor lightemitting device according to claim 9, further comprising an electrode onthe first roughness layer, wherein the electrode has a bottom surfacewith a shape corresponding to the top surface of the second conductivesemiconductor layer.
 14. The semiconductor light emitting deviceaccording to claim 9, wherein the second roughness layer is disposeddirectly on the first roughness layer.
 15. The semiconductor lightemitting device according to claim 9, wherein the first roughness layerincludes an upper surface having a shape corresponding to the topsurface of the second conductive semiconductor layer.
 16. Thesemiconductor light emitting device according to claim 9, wherein thefirst roughness layer has a thickness of about 1000 Å to about 2000 Å.17. The semiconductor light emitting device according to claim 9,further comprising an AlGaN based semiconductor layer disposed on theactive layer.
 18. A light emitting device, comprising: a substrate; afirst conductive semiconductor layer on the substrate; an active layeron the first conductive semiconductor layer; a conductive clad layer onthe active layer, the conductive clad layer comprising an AlGaN-basedlayer; a second conductive semiconductor layer on the conductive cladlayer, the second conductive semiconductor layer including a top surfaceand a bottom surface being close to the second conductive semiconductorlayer, the top surface including a roughness having a random horn shape;a first roughness layer on the roughness of the top surface of thesecond conductive semiconductor layer, the first roughness layer havinga roughness with a random horn shape and being formed of the samematerial as the second conductive semiconductor layer or differentmaterial including Al; a second roughness layer on the first roughnesslayer, the second roughness layer having a roughness with a random hornshape, the second roughness layer comprising a material including Ti;and an electrode on the first roughness layer, the electrode having abottom surface having a roughness with a random horn shape, wherein theroughness of the top surface of the second conductive semiconductorlayer includes a plurality of apexes, the distance between at least twoapexes of the plurality of apexes is in the range of about 0.3 μm toabout 1.0 μm, wherein a distance between one apex of the plurality ofapexes and a valley that is positioned close thereto is in the range ofabout 0.5 μm to about 1.2 μm, wherein the roughness of the firstroughness layer has the same shape corresponding to the roughness of thesecond conductive semiconductor layer, and wherein the roughness of thesecond roughness layer has the same shape corresponding to the roughnessof the first roughness layer.
 19. The light emitting device according toclaim 18, wherein the second roughness layer is disposed directly on thefirst roughness layer.
 20. The light emitting device according to claim18, wherein the first roughness layer has a thickness of about 1000 Å toabout 2000 Å.